The surface properties of objects greatly influence their interaction with the atmosphere, gases, fluids and with biological systems. The relative hydrophobicity and hydrophilicity of a surface significantly affect physical, chemical and biological properties including, but not limited to, friction, wetability, oxidation, interaction with proteins and other molecules, antigenicity and biocompatability.
Millions of surgical procedures are performed each year which require direct contact between living tissues and various surgical instruments, medical devices and prosthetic implants constructed of plastics, polymers, metals such as stainless steel, or materials made from composites of these materials. Despite the many positive benefits which are gained by the use of polymeric compounds for these purposes, there are often serious complications. Plastic and elastomeric, rubbery polymers are generally hydrophobic by nature which means these materials tend to repel, rather than absorb, water. As a result, dynamic contact between the non-water absorbing polymer surfaces and human fluid-based tissues, including blood, can cause significant abrasive damage to fragile and sensitive human cells and tissues. These dynamic contacts can also cause a wide range of undesirable effects such as tissue and cell adhesion, inflammation, thrombogenicity (clotting of the blood), hemolysis, bacterial adhesion and infections, unwanted mineral deposits, and increased pain or limited motion for joint and tendon prostheses.
Materials and fabrics used in the manufacture of clothing, diapers, sanitary napkins, sheets, bedding, sails, furniture, rugs, drapes, car seats and the like are often treated to enhance some property such as hydrophilicity, hydrophobicity or biological reactivity. However, many of the current methods of coating such objects offer only temporary protection and repeated application of protective sprays is often necessary. In addition, many materials have proven especially difficult to modify, decreasing their utility in specific applications such as the manufacture of certain items of clothing or absorbent materials. For example, many have attempted unsuccessfully to modify the surface properties of polypropylene. What is needed is a composition and method to modify materials and fabrics to achieve the desired surface properties.
Exposure of metallic surfaces to solvents such as water, saline and other chemicals may cause chemical oxidation and pitting or wasting of the surface thereby reducing its tensile strength. Oxidative changes also change the surface properties of metals and increase friction with air, liquid and solids. For example, the maritime industry expends vast sums to protect and maintain the outer hulls of ships and other metallic components against the degradative effects of oxidation. Ships with increased surface oxidation of their metallic skins display increased friction with water and air, gradually becoming less efficient. Similar problems affect the aviation, automobile and railroad industries. In addition to the damaging effects of oxidation on the metallic skins of transportation vehicles, the smoothness of their surfaces affects friction and therefore the efficiency and speed. What is needed is a special coating that would enable ships to travel through water with decreased friction, thereby increasing speed and efficiency. Other types of motor vehicles such as automobiles, trucks, and airplanes would become more efficient with a friction reducing coating.
Steel structures such as bridges, buildings, water towers, silos and automobiles also require continual maintenance to protect against the ravages of oxidation induced by air, water, salt and numerous pollutants such as sulfuric acid. What is needed is a composition and method of treating metallic surfaces at the time of their manufacture and also after their incorporation into a product or structure in order to protect the surfaces. What is also needed is a method and composition to maintain structures in order to minimize new and existing oxidation.
Modification of the surface of an object can change the hydrophobic and hydrophilic properties of the surface and may affect physical, chemical and biological properties. Materials may be applied to the surface of objects through various chemical and physical means. The surfaces of objects made of polymers, plastics, metals, ceramics and composite materials have all been modified. One approach involves grafting material onto the surface through the use of gamma ray irradiation which requires special radiation facilities and costly gamma ray sources. In addition to these financial considerations, use of gamma radiation is potentially dangerous to workers exposed to gamma rays during surface modification procedures. Workers using gamma radiation must be monitored routinely for exposure levels to different regions of the body. In addition, special coating applications such as coating the surfaces of large objects may not be amenable to the gamma ray grafting process. Finally, certain types of materials have not been successfully modified due to lack of understanding the relevant parameters or due to competing reactions.
Accordingly, what is needed is a less expensive method of grafting materials onto the surface of objects which does not require special radiation facilities and costly gamma ray sources. What is also needed is a method which does not pose the radiation safety risks inherent in the use of gamma radiation. A method is also needed which is rapid and permits coating of special objects which cannot be coated with conventional processes, and a method which allows great flexibility in the various aspects of the modification relevant to both materials and surfaces.
What is needed is an inexpensive and rapid method of treating the surfaces of devices including, but not limited to, surgical instruments, medical devices, implants, prostheses, and hematology equipment so that the surface tension of the device is reduced thereby decreasing the trauma caused by the device on living tissue and cells.
What is also needed is an inexpensive and rapid method of treating surfaces of materials to be used in the construction of various objects including, but not limited to, buildings, bridges, silos, ships, and motor vehicles such as airplanes, trucks and automobiles, to prevent and retard oxidation. What is also needed is a treatment which will modify the hydrophobic and hydrophilic properties of the surfaces of objects used in the transportation industry to decrease the surface friction. This treatment method should also be amenable to application for routine maintenance of surfaces and for modifying their surface properties.